Conventional control systems often include a central control panel that controls multiple output devices, such as motors, for example. The wiring for each output device is routed back to the central control panel. The output devices are often located up to hundreds of feet away from the central control panel. As such, extensive wiring and conduit are required between the output devices and the central control panels, thereby adding material and labor costs. For example, skilled installers may need to determine wiring schemes from electrical prints, run conduit through the system to the central control panel, route the wires from each device through the conduit, and terminate the wires on the connection in the control panel. Further, troubleshooting such a system often requires a skilled technician to analyze the electrical prints and trace complex wire paths.
Many conventional control systems require most or all of the mechanical system to be in place prior to starting electrical installation. For example, the machines and conduit are installed for the entire or most of the material handling system prior to routing and installing the electrical wires. Such sequential installation of mechanical and electrical components increases the total time required for installation of the system.
The central panel(s) of conventional control systems includes both high and low voltage devices and associated wiring housed in each panel. A panel containing energized high voltage devices may create an arc flash hazard. In many regions and countries, electrical safety codes regulate the safety of high voltage panels. For example, the National Electrical Code (NEC) 2011 and other standards of the National Fire Protection Association (NFPA) provides safety regulations for high voltage control systems in the United States. NFPA 70E, for example, requires the use of proper personal protective equipment (PPE) before an energized panel is opened for maintenance or troubleshooting.
Conventional control systems often include a high voltage safety circuit (e.g., emergency stop or “E-stop” circuit) with safety devices that are wired back to the central control panel. Each safety device is typically wired back to terminals of the central control panel, and the terminals are connected device to device to create a large series safety circuit. Such a large series configuration often leads to voltage drop issues due to the long wire runs. As such, these safety circuits often operate at high voltages, such as 120 volts alternating current (VAC), for example, in an effort to reduce voltage drop issues.
According to an embodiment of the present disclosure, a control module is provided for controlling an output device in a control system. The control module includes a first enclosure containing a plurality of control terminals, a second enclosure containing a controller operative to control an output device, and a communication interface configured to communicate control signals from control terminals of the first enclosure to the controller of the second enclosure to control the output device. A maximum voltage in the first enclosure is less than or equal to a threshold voltage level. A maximum voltage in the second enclosure is greater than the threshold voltage level.
According to another embodiment of the present disclosure, a distributed control system is provided including a main panel with a main controller and a plurality of control modules in communication with the main controller. Each control module is operative to control at least one output device of the control system. Each control module includes a first enclosure that houses a plurality of control terminals, a second enclosure that houses a controller operative to control an output device, and a communication interface operative to communicate control signals from control terminals of the first enclosure to the controller of the second enclosure to control the output device. A maximum voltage in the first enclosure is less than or equal to a threshold voltage level, and a maximum voltage in the second enclosure is greater than the threshold voltage level.
According to yet another embodiment of the present disclosure, a control system is provided including a first control module operative to control an output device of the control system and a second control module operative to control an output device of the control system. The first and second control modules each include a power supply. The control system includes a safety circuit having a plurality of circuit segments. Each circuit segment includes at least one safety device operative to disable an operation of the control system. A first circuit segment is powered by the power supply of the first control module and is coupled to the second control module to control power to the output device controlled by the second control module. The second circuit segment is powered by the power supply of the second control module.
According to still another embodiment of the present disclosure, an emergency stop circuit is provided that is connected to a plurality of control modules of a control system. The emergency stop circuit includes a first circuit segment having at least one safety device operative to disable an operation of the control system and a second circuit segment having at least one safety device operative to disable an operation of the control system. The second circuit segment is connected in series with the first circuit segment. The first circuit segment is coupled to and powered by a power supply of a first control module of the control system, and the second circuit segment is coupled to and powered by a power supply of a second control module of the control system. The first circuit segment is further coupled to the second control module and is operative to enable and disable an operation of the second control module.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.